As part of the manufacture of medical balloon catheters, balloons must be wrapped or folded tightly around the catheter shaft. Typically, balloons are formed into some number (usually 2 to 6) of equal “wings” that are wrapped spirally around the central shaft. Precise wrapping decreases the diameter of the overall catheter balloon, which is important to the catheter's ability to be delivered to the desired site.
The process of wrapping or folding a balloon typically consists of two main steps: a pleating step, in which the wings are formed, and a compression or wrapping step in which the wings are pressed tightly against the catheter shaft and formed permanently into the wrapped shape, usually by both heating and pressure. For both of these steps, the prior art includes several mechanisms and methods. The present invention addresses the pleating step.
One mechanism for pleating a balloon is the “Balloon Folding Fixture” sold by Interface Associates. The mechanism comprises several dies (the number of dies being equal to the desired number of wings) shaped so that, when the dies are moved in unison radially inward toward a centrally-placed, inflated balloon, the balloon is formed into the desired pleated shape. A central cavity is formed when all the dies are moved inward, the cavity having, in cross section, a round shape at the center to accommodate the catheter central shaft, and thin, curved gaps for the wings spiraling outward from the center. Each die is guided by a commercially-available linear guide and driven by a separate stepper motor, with all the linear guides and stepper motors mounted to a common base plate. A shortcoming of this mechanism is that, because of the many parts, attachments, and motor controls that influence the shape and size of the central cavity, the cavity is not sufficiently accurate to repeatably and precisely form the pleated balloon without damage to the balloon.
Another mechanism for pleating a balloon is one used in the “FFS” equipment sold by Machine Solutions Inc., and described in U.S. Pat. No. 6,988,881. The mechanism comprises several dies (the number of dies being equal to the desired number of wings) shaped so that, when the working tips of the dies are moved in unison inward toward a centrally-placed, inflated balloon, the balloon is formed into the desired pleated shape. A central cavity is formed when all the dies are moved inward, the cavity having, in cross section, a round shape at the center to accommodate the catheter central shaft, and thin, curved gaps for the wings spiraling outward from the center. The dies are pivotally coupled to a common base member or hub, and driven in unison by a rotatable drive hub. A shortcoming of this mechanism is that, because of the many parts and attachments that influence the shape and size of the central cavity, the cavity is not sufficiently accurate to repeatably and precisely form the pleated balloon without damage to the balloon.
Another mechanism for pleating a balloon is described in U.S. Pat. No. 6,623,689. In this mechanism, the balloon is pulled axially through a cavity of varying cross section to first form the pleats, then radially compress the balloon. A shortcoming of this method is that the balloon slidingly engages the tooling, introducing a potential for damage to the balloon by scratching or abrasion.
Another mechanism for pleating a balloon is described in U.S. Pat. No. 5,783,227. In this mechanism, two die halves are moved inward toward a centrally-placed, inflated balloon, forming the balloon into a two-pleated shape. A central cavity is formed when all the dies are moved inward, the cavity having, in cross section, a round shape at the center to accommodate the catheter central shaft, and thin, radially-outward gaps for the wings. A shortcoming of this mechanism is that only two wings can be formed in the balloon.
It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.
Accordingly, it is an object of the present invention to provide a new and improved balloon pleating mechanism.
Another object of the invention is to provide a new and improved balloon pleating mechanism for pleating balloons for use in devices such as stents, catheters, and the like in the medical industry.
Another object of the invention is to provide a new and improved balloon pleating mechanism that accurately and repeatably pleats balloons used in the medical industry without damaging or weakening the balloons.